Bacterial purine signaling pathway modulates C. elegans development and stress tolerance via DAF-16

The purine signaling pathway is crucial for cellular function and is a conserved metabolic network from prokaryotes to humans. While extensively studied in microorganisms like yeast and bacteria, the impact of perturbing dietary intermediates from the purine signaling pathway on animal development and growth remains poorly understood. We utilized Caenorhabditis elegans as the metazoan model to investigate the mechanisms underlying this deficiency. Through a high-throughput screening of an E. coli mutant library Keio collection, we identified 34 E. coli mutants that delay C. elegans development. Among these mutants, we found that E. coli purE gene is an essential genetic component that promotes host development in a dose-dependent manner. Further metabolites supplementation suggests that bacterial purE downstream metabolite 5-aminoimidazole-4-carboxamide ribotide (AICAR) can inhibit worm growth. Additionally, we found the FoxO transcription factor DAF-16 is indispensable in worm development delay induced by purE mutation, and observed increased nuclear accumulation of DAF-16 when fed E. coli purE- mutants, suggesting the role of DAF-16 in response to purE mutation. RNA-seq analysis and phenotypic assays revealed that worms fed the E. coli purE mutant exhibited elevated lifespan, thermotolerance, and pathogen resistance. These findings collectively suggest that certain intermediates in the bacterial purine signaling pathway can serve as a cue to modulate development and activate the defense response in the nematode C. elegans through DAF-16. Overall design: Synchronized L1 stage C. elegans worms were grown on NGM agar plates seeded with E. coli BW25113 bacteria. After reaching the desired developmental stage, worms were transferred to NGM agar plates with either wild-type E. coli BW25113 or the E. coli purE mutant. Following a 48-hour feeding period, worms underwent a 2-hour diet switch.